Araz Gholami

In November 2002, the World Wide Web Consortium proposed OWL as a semantic markup language for publishing and sharing web ontologies. OWL is based on RDF and derived from DAML+OIL. It is one of the semantic markup languages that uses clear and formal definitions of classes, instances, and relationships in ontology development. Compared to XML, RDF, and RDFS, OWL provides more capabilities to express concepts and meanings, making it superior for representing machine-interpretable content on the web. OWL has three sublanguages: OWL Lite, OWL DL, and OWL Full, each designed with specific features for different user groups.

The term ontology has Latin roots, from "onto" meaning existence and "logia" meaning knowledge or study, essentially translating to "the study of being." The first part refers to existence, and the second to individual understanding, which ancient Greeks sought. Ontology in AI describes explicit, shared, and formal representations of concepts and relationships across a domain. Thomas Gruber defined modern ontologies as formal specifications of a conceptualization, expressed in a language that computers can process.

Web Ontology Language (OWL) is a markup language designed to publish and exchange knowledge on the web's semantic layer. Developed by Mike Dean and Guus Schreiber in 2002, OWL bridges philosophy and computer science. The second version was released on November 12, 2009.

OWL models domain-specific knowledge as a family of interrelated concepts with hierarchical inclusion relationships. Information is structured in a tree, becoming more specialized at deeper levels.

OWL ontologies are classified into three sublanguages based on expressiveness:

• OWL Lite: The least expressive of the three.
• OWL DL: Offers expressiveness between OWL Lite and OWL Full.
• OWL Full: The most expressive variant.

Download the optimized OWL Web Ontology Language Guide.
For complete reference and further information, visit the World Wide Web Consortium.